修复清除缓存显示"已释放约0.0MB"，与实际清理量不符

现象：设置-清除缓存确认后，无论Cache Storage里实际有多少数据，展示的"已释放约
X MB"几乎总是0.0，即使清理动作本身（caches.delete）确实生效（caches.keys()清理后
变为空数组）。

根因：原实现在caches.delete()前后各调用一次navigator.storage.estimate()，用两次
usage之差算释放量。实测确认Chrome的storage.estimate()不会同步反映Cache Storage的
删除——caches.keys()已经确认清空后，estimate()仍继续报告删除前的usageDetails.caches
数值，实测滞后超过500ms未刷新。人为塞入一个2MB的Cache Storage测试项复现：删除成功
但"已释放"显示0.0MB；塞入3MB项验证修复后正确显示3.0MB。

修法：不再依赖storage.estimate()的前后差值，改成删除前逐个遍历所有Cache
Storage条目、读取每个response的真实blob大小并累加，直接得到本次会话即将删除的
真实字节数，不受浏览器存储统计滞后影响。

验证：npm run build:dev后浏览器实测——(1) 无缓存数据时点击"清除缓存"，正确显示
0.0MB且弹层能正常从"清空缓存"态切到"缓存已清理"态、点"完成"可关闭；(2) 用JS人为写入
2MB/3MB测试用Cache Storage条目，分别清理后弹层准确显示2.0MB/3.0MB，且caches.keys()
确认条目已被真实删除。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/views/personal-settings-view.jsx

@@ -367,20 +367,40 @@ function CacheClear({onToast, onClose}) {
   const confirm = async () => {
     setBusy(true);
     try {
-      // navigator.storage/caches can be entirely absent (private browsing in some browsers, older
-      // WebViews) rather than just rejecting -- referencing a missing global throws synchronously,
-      // which a bare .catch() on the call below can't catch (it never gets that far), so without
-      // this check the whole confirm() throws, `done` never becomes true, and the "已完成" state is
-      // never reached even though the button correctly stops spinning via `finally`.
-      const hasStorageEstimate = typeof navigator !== 'undefined' && navigator.storage && navigator.storage.estimate;
+      // Was a before/after navigator.storage.estimate() diff around the caches.delete() call --
+      // measured live (see this round's regression notes): estimate() does NOT reflect a deletion
+      // synchronously, Chrome keeps reporting the pre-delete `usageDetails.caches` figure for well
+      // over 500ms after `caches.keys()` already comes back empty. Every real run of this button
+      // therefore computed `before - after` from two numbers that were still identical, landing on
+      // "已释放约 0.0 MB" even when megabytes of real thumbnails/temp files were actually deleted --
+      // confirmed by seeding a 2MB dummy Cache Storage entry and watching this path report 0.0 MB
+      // freed for it. Summing each entry's real blob size before deleting it sidesteps the OS-level
+      // storage accounting lag entirely -- the number shown is exactly what this run deleted, not an
+      // estimate that may or may not have caught up yet.
+      // caches can be entirely absent (private browsing in some browsers, older WebViews) rather than
+      // just rejecting -- referencing a missing global throws synchronously, which a bare .catch() on
+      // the call below can't catch (it never gets that far), so without this check the whole
+      // confirm() throws, `done` never becomes true, and the "已完成" state is never reached even
+      // though the button correctly stops spinning via `finally`.
       const hasCaches = typeof caches !== 'undefined';
-      const before = hasStorageEstimate ? (await navigator.storage.estimate().catch(() => ({usage: 0}))).usage || 0 : 0;
+      let freedBytes = 0;
       if (hasCaches) {
         const keys = await caches.keys();
+        for (const key of keys) {
+          const cache = await caches.open(key);
+          const requests = await cache.keys();
+          for (const request of requests) {
+            const response = await cache.match(request);
+            if (!response) continue;
+            // clone() -- match() gives back the one real (non-clonable-twice) body for this entry;
+            // reading .blob() off it directly would leave nothing for a concurrent reader of the
+            // same cache, however unlikely that is here.
+            freedBytes += (await response.clone().blob().catch(() => null))?.size || 0;
+          }
+        }
         await Promise.all(keys.map(k => caches.delete(k)));
       }
-      const after = hasStorageEstimate ? (await navigator.storage.estimate().catch(() => ({usage: 0}))).usage || 0 : 0;
-      setFreed(Math.max(0, before - after));
+      setFreed(freedBytes);
       setDone(true);
     } catch (err) {
       onToast(err.message || '清理失败，请重试');